Identifying candidate Aspergillus pathogenicity factors by annotation frequency

Analysis of fungal composition in different layers of Bantou agarwood-forming trunk of Aquilaria sinensis revealing presence of Aspergillus-inhibiting substances in agarwood sites

Objective

The objective of this study was to analyse fungal composition and exploit application potential in the Bantou (BT) agarwood-forming trunk of Aquilaria sinensis.

Methods

BT agarwood is a naturally formed agarwood that was collected after cutting. Total genomic DNA of the fungi in BT agarwood was extracted by the hexadecyltrimethy ammonium bromide (CTAB) method, followed by PCR amplification and library construction. The effective tags were obtained by the HiSeq2500 platform, and the data were subjected to bioinformatics and statistical analyses.

Results

A total of 7 850 040 effective tags were obtained, Ascomycota was the most abundant fungus at the phylum level, with a relative abundance of 56.36%-61.44%, followed by Basidiomycota, with a relative abundance of 10.49%-20.39%. Dothideomycetes, Agaricomycetes and Sordariomycetes were dominant at the class level, accounting for 26.21%-33.88%, 8.40%-17.66%, and 18.41%-24.11%, respectively. Lignosphaeria, Phaeoacremonium and Hermatomyces were dominant at the genus level, with relative abundances of 6.25%-7.64%, 1.95%-9.05% and 1.5%-5.4%, respectively. Diversity and richness analysis showed that the fungal composition in the agarwood formation sites (agarwood layer, upper agarwood layer and lower agarwood layer) were significantly lower than those in the decomposing layer and the healthy layer. That is, the fungal diversity and richness were significantly reduced during agarwood formation by the action of open wounds. The fungal community structure in the decomposing layer and agarwood formation sites obviously differed from that in the healthy layer. The number of Aspergillus taxa in agarwood formation sites decreased significantly (healthy layer is 0.5%, decomposing layer is 0.022%, upper agarwood layer is 0.012%, agarwood layer is 0.01%, and lower agarwood layer is 0.013%), indicating that agarwood may contain potential substances to inhibit the growth of Aspergillus.

Conclusion

Agarwood from agarwood formation sites contains potential substances that inhibit Aspergillus, which provides valuable information for the control of the genus of Aspergillus.

The Essentials of PgPG1, a Polygalacturonase-Encoding Gene for the Invasion of Pyrenophora graminea to Hordeum vulgare

Barley leaf stripe, caused by Pyrenophora graminea, significantly reduces yield. Polygalacturonase, a key fungal pectinase, facilitates cell wall degradation for nutrition acquisition and colonization. To determine whether P. graminea contains polygalacturonase (PgPG)-encoding genes and their role in pathogenicity, four PgPG genes (PgPG1-PgPG4) were identified in the P. graminea genome. Quantitative RT-PCR revealed that PgPG1 had the highest inducible expression during barley infection, suggesting its critical vital role in pathogenesis. PgPG1 was silenced and overexpressed in P. graminea QWC (wild-type) using CaCl2-PEG4000-mediated protoplast transformation. The PgPG1 RNAi mutants exhibited slower growth, while overexpression mutants grew faster. Relative to the wild-type, the disease incidence of Alexis, a highly susceptible barley variety, decreased by 62.94%, 42.19%, 45.74%, and 40.67% for RNAi mutants, and increased by 12.73%, 12.10%, 12.63%, and 10.31% for overexpression mutants. Pathogenicity analysis showed decreased disease incidence with PgPG1 RNAi mutants and increased severity with overexpression mutants. Trypan blue staining and polygalacturonase activity assays confirmed that overexpression mutants caused more severe damage compared to wild-type and RNAi mutants. These findings indicate that PgPG1 plays a vital role in the pathogenicity of P. graminea in barley and has great potential as a pathogen target gene to develop a durable resistance variety to P. graminea.

Culture-dependent methods reveal the diversity of endophytic fungi of Psidium cattleianum leaves (Myrtales: Myrtaceae)

Endophytic fungi are a diverse group of microorganisms that reside within plant tissues and play a crucial ecological role in the development of their hosts. Psidium cattleianum (Myrtales: Myrtaceae: 'Cattley guava') is a Brazilian native species with economic potential due to the diverse applications of its fruits, wood, and essential oils. Despite their significance, the diversity of endophytic fungi associated with P. cattleianum remains unexplored. Here, we investigated the diversity of endophytic fungi in the leaves of this plant using cultivation-dependent isolation methods, analysis of the macroscopic characters of the isolates, and phylogenetic analyses employing the ITS barcode marker. A total of 396 isolates, classified into 25 fungal taxa, were obtained, namely, Alternaria, Aspergillus, Cladosporium, Colletotrichum, Coprinellus, Coriolopsis, Diaporthe, Induratia, Mycosphaerella, Muyocoprom, Myrmecridium, Neofusicoccum, Pantospora, Paracamarosporium, Parapallidocercospora, Paraphaeosphaeria, Penicillium, Perenniporia, Phaeophleospora, Phyllosticta, Pseudofusicoccum, Talaromyces, Xylaria, Sordariomycetes, and Xylariomycetes. Our findings reveal a significant diversity of fungi associated with P. cattleianum leaves; however, our study suggests an even greater diversity of fungi associated with this plant species. Interestingly, although P. cattleianum shares endophytic fungi with other plants in the Myrtaceae family, this plant species harbors a unique fungal community. This distinction is evidenced by certain fungal genera and seven potentially new phylogenetic species, isolated in this study.

Microbial Pathogens in Aquaponics Potentially Hazardous for Human Health

The union of aquaculture and hydroponics is named aquaponics-a system where microorganisms, fish and plants coexist in a water environment. Bacteria are essential in processes which are fundamental for the functioning and equilibrium of aquaponic systems. Such processes are nitrification, extraction of various macro- and micronutrients from the feed leftovers and feces, etc. However, in aquaponics there are not only beneficial, but also potentially hazardous microorganisms of fish, human, and plant origin. It is important to establish the presence of human pathogens, their way of entering the aforementioned systems, and their control in order to assess the risk to human health when consuming plants and fish grown in aquaponics. Literature analysis shows that aquaponic bacteria and yeasts are mainly pathogenic to fish and humans but rarely to plants, while most of the molds are pathogenic to humans, plants, and fish. Since the various human pathogenic bacteria and fungi found in aquaponics enter the water when proper hygiene practices are not applied and followed, if these requirements are met, aquaponic systems are a good choice for growing healthy fish and plants safe for human consumption. However, many of the aquaponic pathogens are listed in the WHO list of drug-resistant bacteria for which new antibiotics are urgently needed, making disease control by antibiotics a real challenge. Because pathogen control by conventional physical methods, chemical methods, and antibiotic treatment is potentially harmful to humans, fish, plants, and beneficial microorganisms, a biological control with antagonistic microorganisms, phytotherapy, bacteriophage therapy, and nanomedicine are potential alternatives to these methods.

Structural adaptation of fungal cell wall in hypersaline environment

Halophilic fungi thrive in hypersaline habitats and face a range of extreme conditions. These fungal species have gained considerable attention due to their potential applications in harsh industrial processes, such as bioremediation and fermentation under unfavorable conditions of hypersalinity, low water activity, and extreme pH. However, the role of the cell wall in surviving these environmental conditions remains unclear. Here we employ solid-state NMR spectroscopy to compare the cell wall architecture of Aspergillus sydowii across salinity gradients. Analyses of intact cells reveal that A. sydowii cell walls contain a rigid core comprising chitin, β-glucan, and chitosan, shielded by a surface shell composed of galactomannan and galactosaminogalactan. When exposed to hypersaline conditions, A. sydowii enhances chitin biosynthesis and incorporates α-glucan to create thick, stiff, and hydrophobic cell walls. Such structural rearrangements enable the fungus to adapt to both hypersaline and salt-deprived conditions, providing a robust mechanism for withstanding external stress. These molecular principles can aid in the optimization of halophilic strains for biotechnology applications.

Oro-facial Mycoses in Coronavirus Disease-2019 (COVID-19): A Systematic Review

Objectives

Studies reviewing orofacial mycoses in coronavirus disease-2019 (COVID-19) caused by severe acute respiratory syndrome 2 (SARS-CoV-2) infection are sparse. Here we review the major oral and maxillofacial mycoses of COVID-19, the associated comorbidities, and the probable precipitating factors.

Methods

English-language manuscripts published between March 2020 and October 2021 were searched using PubMed, OVID, SCOPUS, and Web of Science databases, using appropriate keywords.

Results

We identified 30 articles across 14 countries, which met the inclusion criteria of PRISMA guidelines. These yielded a total of 292 patients with laboratory-confirmed COVID-19, 51.4% (n = 150) of whom presented with oral and maxillofacial fungal infections, mainly comprising candidosis, mucormycosis, and aspergillosis. Candida infections were the most prevalent, present in 64% (n = 96), followed by mucormycosis, and only a single case of aspergillosis was noted. Oral and maxillofacial mycoses were predominantly seen in those with comorbidities, especially in those with diabetes (52.4%). Oral mucormycosis was noted in 8.6% (n = 13) and mainly manifested on the hard palate. An overall event rate of oral/maxillofacial mucormycosis manifestation in patients with COVID-19 with diabetes mellitus type 1/2 was about 94% (49/52; 95% confidence interval, 0.73%-0.89%), implying a very high association between diabetes mellitus and the latter condition. All fungal infections appeared either concurrently with COVID-19 symptoms or during the immediate recovery period.

Conclusions

SARS-CoV-2 infection–related immunosuppression, steroid therapy, as well as comorbidities such as diabetic hyperglycemia appear to be the major predisposing factors for the onset of oral and maxillofacial mycoses in patients with COVID-19 across all age groups.

Composition and Diversity of the Culturable Endophytic Community of Six Stress-Tolerant Dessert Plants Grown in Stressful Soil in a Hot Dry Desert Region

Saudi Arabia is part of a hot dry desert region and is characterized by stressful conditions. The main goal of this research was to identify endophytic fungal (EF) community composition, diversity and abundance in relation to their plant hosts and soil stress. The above-ground parts of six wild plants (Haloxylon salicornicum, Salsola kali, Heliotropium bacciferum, Erica verticillata, Salsola imbricata and Bienertia sinuspersici) were sampled, surface-sterilized and cut into small pieces, which were cultured and incubated for 4–6 weeks. Isolates were grouped and identified by using both morphological and ITS rDNA molecular data. The diversity and community structure of plant-endophyte associations were studied. A total of 455 EF isolates were grouped into 25 different taxa; 21 of which were identified at the species level, 2 at genus level and 2 were unclassified fungi. Here, 95.65% of the identified genera were Ascomycota; of which 36.36, 31.81 and 31.81% were members of the classes Dothideomycetes, Eurotiomycetes and Sordariomycetes, respectively. S. imbricata showed the highest isolation rate and colonization frequency (CF%) of EF when compared to other plant species. Additionally, S. imbricata demonstrated the highest species richness and species diversity of the EF community predominated by the genus Fusarium. Conclusively, the core culturable EF genera of six wild plants were identified (unculturable taxa were not identified in this study). The composition of the EF community was revealed to have a strong correlation to both the electrical conductivity and pH of the soil and a moderate correlation to both the host species and the host family. The abundance and diversity of EF communities of the six plants were environment-dependent.

Genomic and Phenotypic Analysis of COVID-19-Associated Pulmonary Aspergillosis Isolates of Aspergillus fumigatus

The ongoing global pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for coronavirus disease 2019 (COVID-19), first described in Wuhan, China. A subset of COVID-19 patients has been reported to have acquired secondary infections by microbial pathogens, such as opportunistic fungal pathogens from the genus Aspergillus. To gain insight into COVID-19-associated pulmonary aspergillosis (CAPA), we analyzed the genomes and characterized the phenotypic profiles of four CAPA isolates of Aspergillus fumigatus obtained from patients treated in the area of North Rhine-Westphalia, Germany. By examining the mutational spectrum of single nucleotide polymorphisms, insertion-deletion polymorphisms, and copy number variants among 206 genes known to modulate A. fumigatus virulence, we found that CAPA isolate genomes do not exhibit significant differences from the genome of the Af293 reference strain. By examining a number of factors, including virulence in an invertebrate moth model, growth in the presence of osmotic, cell wall, and oxidative stressors, secondary metabolite biosynthesis, and the MIC of antifungal drugs, we found that CAPA isolates were generally, but not always, similar to A. fumigatus reference strains Af293 and CEA17. Notably, CAPA isolate D had more putative loss-of-function mutations in genes known to increase virulence when deleted. Moreover, CAPA isolate D was significantly more virulent than the other three CAPA isolates and the A. fumigatus reference strains Af293 and CEA17, but similarly virulent to two other clinical strains of A. fumigatus. These findings expand our understanding of the genomic and phenotypic characteristics of isolates that cause CAPA. IMPORTANCE The global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent of coronavirus disease 2019 (COVID-19), has already killed millions of people. COVID-19 patient outcome can be further complicated by secondary infections, such as COVID-19-associated pulmonary aspergillosis (CAPA). CAPA is caused by Aspergillus fungal pathogens, but there is little information about the genomic and phenotypic characteristics of CAPA isolates. We conducted genome sequencing and extensive phenotyping of four CAPA isolates of Aspergillus fumigatus from Germany. We found that CAPA isolates were often, but not always, similar to other reference strains of A. fumigatus across 206 genetic determinants of infection-relevant phenotypes, including virulence. For example, CAPA isolate D was more virulent than other CAPA isolates and reference strains in an invertebrate model of fungal disease, but similarly virulent to two other clinical strains. These results expand our understanding of COVID-19-associated pulmonary aspergillosis.